The Chicago Manual of Style (CMS) covers both the Notes-Bibliography System (NB), used primarily in the humanities and the Author-Date System (AD), used primarily in the social sciences.
Used primarily in the behavioral sciences, the Manual includes information on writing, style, displaying results, citing sources, key reference works and the publication process.
MLA - Modern Language Association
MLA Handbook, 8th ed.
Used throughout the natural and physical sciences and developed by the Council of Science Editors (CSE), Scientific Style and Format includes information on Publishing Fundamentals, General Style Conventions, Special Scientific Conventions, and Technical Elements of Publications.